In general, emulsion-polymerized heat-resistant SANs have advantages such as high Tg and high molecular weight, but disadvantages such as decreased workability and productivity due to long polymerization time, high temperature during coagulation/drying processes, and a pressing process.
Accordingly, methods such as a method of enhancing polymerization speed by increasing the amounts of an emulsifier and an initiator and a method of enhancing cohesion through addition of an organic solvent, etc. have been attempted. However, by increasing the amounts of an emulsifier and an initiator, impurities derived from these additives and a generated oligomer amount are increased, whereby a decrement of Tg increases. In addition, cohesion enhancement due to addition of an organic solvent may cause workability decrease due to volatilization of the organic solvent and intrinsic heat-resistant characteristics may be deteriorated by Tg decrease due to a remaining organic solvent.
Therefore, there is an urgent need for technology to maintain intrinsic heat resistance while securing a polymerization rate and cohesion.